Hello,
I have done that, I have enabled NAT in the polycom device, configured the Inbound Rules in the Application Switches for TCP 1720, 1718UDP, 1719, 3230-3235TCP and 3230-3253UDP. Configured filter to bypass the proxy ISA Server but that didn't success at all. I can dial, the other end can hear me and see me, but I can't get anything from the far site.
Tried that with Untangle set in front of ADSL Cisco Router with two interfaces, External 192.168.50.x and Internal 192.168.10.x then configured the polycom device to map the gateway as the Internal device of the Untangle, same connection established, but can't receive. I have tried the same setup also with TMG and ISA Server 2006 also no joy...
The only remaining setup I have to make to connect the Polycom device directly into the ADSL router and test..

That can't do it because it's far from the building... Hummmm, I can test that way by hocking the ADSL into the production network using second interface of the ADSL Router, create a VLAN into the Switch and extend it to the Core Switch. Then, extend this vLAN to the Switch where the Polycom device connected and configure the port into the switch where the Polycom device connected to use the ADSL vLAN... Let me see that gonna work or not...
Thanks,